Abstract: There is provided a copper alloy which comprises 1.0 to 3.5 wt. % of Ni, 0.2 to 0.9 wt. % of Si, 0.02 to 1.0 wt. % of Mn, 0.1 to 5.0 wt. % of Zn, 0.1 to 2.0 wt. % of Sn, and 0.001 to 0.01 wt. % of Mg, and 0.001 to 0.01 wt. % of one or more members selected from Cr, Ti, and Zr, with the remainder being substantially Cu. The copper alloy is suitable for lead frames for semiconductors and is also suitable for terminals and connectors. The copper alloy is produced by a process which comprises starting cooling from a temperature above 600.degree. C. at a rate of 5.degree. C. per second or higher after hot rolling of an ingot of said copper alloy, performing annealing at a temperature of 400.degree. to 600.degree. C. for 5 minutes to 4 hours after cold working, performing refining finish rolling, and performing annealing at a temperature of 400.degree. to 600.degree. C. for a short time of 5 to 60 seconds.